Design of CNS-Permeable Agents for the Treatment of Lipid Storage Diseases

描述（由申请人提供）：超过75种不同的溶酶体蛋白已被表征。其中42种蛋白质的基因突变与溶酶体贮积病有关。在这些疾病中，14种是鞘脂分解代谢受损的结果，其中7种是由于鞘脂糖降解受损。这些疾病包括I型戈谢病、法布里病和各种中枢神经系统疾病。治疗鞘糖脂病的传统方法是以甘露糖终止糖苷酶的形式使用酶替代疗法。这一策略虽然在治疗Fabry和Gaucher病的外周表现方面取得了成功，但对于Tay-Sachs病和Sandhoff病等基于中枢神经系统的疾病无效。迄今为止，包括基因疗法和骨髓移植在内的其他形式的酶替代疗法都令人失望。另一种策略是通过使用糖鞘脂转移酶的小分子抑制剂来抑制糖鞘脂的生物合成，最明显的是葡萄糖神经酰胺合成酶。基于PDMP的葡萄糖神经酰胺类似物代表了葡萄糖神经酰胺合成酶抑制剂的范例类。这些化合物是由密歇根大学的Shayman和Radin实验室发现并鉴定的，已被许多研究小组广泛用于探测糖脂的功能。一种PDMP同系物d -三乙基二氧苯-2-辛烷氨基-3-吡咯烷二丙醇目前正在I型戈谢病的II期试验中。然而，迄今为止表征的PDMP同源物已证明对中枢神经系统的渗透性差，限制了它们对外周组织的潜在效用。据推测，现有的PDMP类有效的葡萄糖神经酰胺合成酶抑制剂可以在不牺牲药效团关键元素的情况下进行结构修饰，以达到渗透到中枢神经系统的目的。进一步假设，开发有效的具有有效中枢神经系统通透性的糖基神经酰胺合成酶小分子抑制剂将显著扩大可治疗的鞘糖脂病的范围。为了实现这些目标，PDMP模板的选择性质（例如分子量，极性表面积和可旋转键的数量）将被修改，以更接近中枢神经系统药物的性质，使用计算模型来指导设计。新化合物将在无细胞和全细胞试验中测试抑制鞘糖脂合成的效力。对被动细胞渗透性、P-gp介导的外排和血浆蛋白结合的评估将用于预测有效的中枢神经系统渗透，并优先考虑进行体内试验的化合物。

DESCRIPTION (provided by applicant): Greater than seventy-five distinct lysosomal proteins have been characterized. Genetic mutations of forty-two of these proteins are associated with lysosomal storage diseases. Of these diseases, fourteen are the result of impaired catabolism of sphingolipids and seven of these are due to impaired degradation of glycosphingolipids. These disorders include type I Gaucher disease, Fabry disease, and various central nervous system based diseases. The traditional approach to the treatment of glycosphingolipidoses has been to use enzyme replacement therapy in the form of mannose terminated glycosidases. This strategy, although successful for the treatment of the peripheral manifestations of Fabry and Gaucher disease, is ineffective for CNS based disorders such as Tay-Sachs and Sandhoff disease. Other forms of enzyme replacement, including gene therapy and bone marrow transplantation have been disappointing to date. An alternative strategy has been the inhibition of glycosphingolipid biosynthesis by the use of small molecule inhibitors of glycosphingolipid transferases, most notably glucosylceramide synthase. The PDMP based glucosylceramide analogues represent the paradigm class of glucosylceramide synthase inhibitors. These compounds, discovered and characterized by the Shayman and Radin labs at the University of Michigan, have been widely used by many groups to probe the functions of glycolipids. One PDMP homologue, D-threo-ethylendioxyphenyl-2- octanoylamino-3-pyrrolidino-propanol, is currently in phase II trials for type I Gaucher disease. The PDMP homologues characterized to date, however, have demonstrated poor penetration of the CNS, limiting their potential utility to peripheral tissues. It is hypothesized that the existing PDMP class of potent glucosylceramide synthase inhibitors can be structurally modified to achieve penetration into the CNS without sacrificing key elements of the pharmacaphore. It is further hypothesized that the development of potent small molecule inhibitors of glucosylceramide synthase with efficient CNS permeability will significantly expand the scope of treatable glycosphingolipidoses. Toward these objectives, selected properties of the PDMP template (e.g. molecular weight, polar surface area and number of rotatable bonds) will be modified to more closely approximate those of CNS drugs, using computational models to guide the design. New compounds will be tested in both cell-free and whole cell assays for potency at inhibiting glycosphingolipid synthesis. Evaluations of passive cellular permeability, P-gp mediated efflux and plasma protein binding will be used to predict efficient CNS penetration and to prioritize compounds for in vivo testing. PUBLIC HEALTH RELEVANCE: Current therapy for rare but severely debilitating heritable lipid storage diseases is limited to peripheral tissues, leaving patients with CNS-based lipidoses, including Tay-Sachs, Fabry and Gaucher Types II and III, without effective treatment. Substrate reduction therapy via inhibition of glycosphingolipid biosynthesis holds promise for the treatment of CNS-based lipidoses if agents can be developed that efficiently penetrate the CNS. This proposal will evaluate the feasibility of modifying an established class of small molecule inhibitors of glucosylceramide synthase to achieve potency, specificity and blood brain barrier permeability.